Tension device for sewing machines



March 22, 1932. E, E, w Y 1,850,611

TENSION DEVICE FOR SEWING MACHINES Filed May 7, 1930 2 Sheets-Sheet 1ili'z'rzeaa' V jvengaj/ Patented Mar. 22, 1932 lTE-D STATESPArENrFor-FicIE ERASTUS E. WINKLEY, 0F LYNN, MASSACHUSETTS; .ASSIGNOR TOUNITED SHOE .MA-

GHINERY COBIPGBATION, OF PAT ERSON, NEW JERSEY, A COEPORATIONOF NEW.

JERSEY TENSION DEVICE FOR SEWING MACHINES Application filed May 7, 1930.Serial No. 450,420.

The present invention has relation to sewing machines, and in particularto the tension devices which are applied to such machines to control thethread during the setting of ,5; the stitch, and at other times in theoperation of the sewing machine.

Devices of many sorts have been employed to put tension upon the threadin such machines, the commonest forms of tension delo; vices employingfriction to hold back the travel of the thread as drawn from the supplyby the stitch forming'devices or otherwise, until the desired degree oftension has been attained in the thread. lhe friction has been appliedin general through two different arrangements. In the -one,-thethread'has been drawn between or around surfaces in such manner that thethread slips or slides rela-' in the common form of tension device in 2.1 which a movable presser squeezes the thread against a stationaryabutment under a strong pressure, and the thread is drawn from betweenthe two, it is commonly found that the rubbing of these opposed surfacesagainst op the twist in the thread in the direction of the supply, untilsuch' twist accumulates to the extent and degree where it forces its waythrough the tension devices. The thread. thickened and rendered harderby this accumulated twist, meets with more resistance in being drawnthrough the tension device, and hence is moved forward with increasedeffort by the thread handling and stitch forming devices, resulting inuneven setting of the stitches and unsatisfactorw appearance of thefinished seam. As to the other class of device, in which the friction isapplied to a member whose surface moves'with Q1the thread, as in thecase of the familiar .posite sides of the thread tends to run backrotating tension wheel having a brake resisting its rotation, there isnot the tendency to run back the twist, but the vperformance of suchdevices leaves room for improvement in that they are i incapable ofretrieving any slack momentarily and incidentally occurring in thethread between such tension device and the work.

It is one object of the present invention to improve the operation oftension devices in these respects, so as to provide a novel device ofthis class capable of handling twisted thread with-out any tendencyto-run back the twist and also adapted to retrieve any slack occurringbetweenit and the work during its plariod of operation in the cycle ofthe mac me.

It is a further object of the present invention to provide novel andimproved mechanism for tensioning-the thread leading from the supplyduring the operation of the stitch-forming devices adapted to maintain aconstant tension of a predetermined amount on the thread leading to thestitch-forming devices which will be independent of any variations inthe resistance offered to the passage of the thread fromthe supply tothe ten-' sioning mechanism.

NVith the above objects in view, one feature of the inventionconsists'in the provision of tension devices for sewing machines havingthread'clampin-g means which are adapted to engage the thread and travelalong with it as it is drawn from the supply, such thread clamping meansbeing adapted to resist yieldingly the forward movement of the threadand adapted to release the thread at the.

proper point in the cycle of the machine and reengage the thread atafmore remote point knots, variations in the thickness of the thread, orvariation in the consistency and distribution of the wax which must bestripped off by the stripper.

In order to eliminate more completely the variations in the tension andthe consequent irregularities and defects in the finished stitching, thepresent invention further contemplates the provision of a threadpull-off cooperating with the thread clamping devices herein disclosedto pull off the requisite amount of thread from the supply through thewax pot and stripper prior to the movement of the clamping means withthe thread during the needle loop drawing stroke.

An embodiment of the invention in its preferred form is shown in thedrawings, applied merely for purposes of'illustration to a well-knowntype of sewing machine. In the drawings Fig. 1 is a side elevation of aMcKay type of sewing machine, with the invention applied thereto; Fig. 2is a view of certain parts shown in Fig. 1, also in side elevation andon a large scale; Fig. 3 is a front sectional view, of the parts of Fig.2.

-Having reference to the drawings, the machine indicated in Fig. 1 is atypical McKay type chain stitch shoe sewing machine such as is shown anddescribed in U. S. Letters Patent No. 1,177,581 granted on March 28,1916 to W. C. Meyer, to which patent reference may be had for a full andcomplete deseri tion of the construction and operation of t e machine,and of such parts as are not dealt with in the present specification.

The tension device is shown applied to the machine to engage the threadjust as it emerges from the wax pot 2 and just prior to its entry intothe end of the hollow shaft 4 comprising one of the series of shaftstransmitting power from the cam shaft of the machine to rotate the usualwhirl 5 located in the tip of the horn 6 which serves to place thethread in the hook or barb of the needle 7.

j The novel tension device comprises threadclamping jaws adapted to gripthe thread and to travel along with it without relative motion withrespect to the thread while acting to create tension. The jaws areconstituted by-the cooperating end-portions of a pair of arms 8 and 28,pivoted together at 26 and swinging as a unit about a pivot pin 10rotating in the hub 12 of a bracket 14 that is fixed to the bracket 16which is applied to the side of the column 18 and supports the horn 6and other parts. The arms are adapted to swing through an arc ofconsiderable amplitude in the vertical plane of the thread as the latterstretches from the stripper 20 of the wax pot to the hollow shaft 4. Theend of the'arm 8 is provided at its opposite edges with lugs 22 providedwith guide holes through which the thread passes. Lugs 24 on the arm 8support the pivot 26 upon which is mounted the second arm 28, theextremity of which enters between the thread guiding lugs 22 to engagethe thread in its passage across the intervening surface of the arm 8.An axial bore 80 in the end of the ivot 10 of arm 8 contains a plunger32 presse outwardly by a spring 34 and bearing against the under surfaceof one end of the arm 28 to force the latters opposite end against thethread guiding extremity of the arm 8, so as to seize and clamp thethread firmly where it extends across the surface of the arm 8.

The hub 12 of bracket 14 is provided with a projecting hollow studthrough which the pin 10 extends and about which is coiled a spring 38having one of its ends fixed in the hub 12 and its other secured in acollar 40 adj ustably fixed on the pivot pin 10 on which the arm 8 ismounted. This spring acts to hold the two arms swung downwardly with theside of arm 8 resting against a sto pin 42 in an extension of thebracket 14. rom this depressed position the tension drive is adapted tobe swung upward through its grip upon the thread for a distancedetermined by the amount of thread drawn from the supply by thestitch-forming devices of the machine during each cycle of operation.

The thread clamping jaws are released to free the thread from tension,as the needle reaches its farthest retracted position in drawing a loopof thread through the work. To effect this release, the end of arm 28 ispressed inwardly against the resistance of its spring plunger 32 tospread the clamping jaws and release the thread, and this operation iseffected at the proper moment in the cycle of the machine by means of arocker lever 44 carried on a stud 46 mounted in the bracket 16, one ofits arms having a cam roll 48 engaging with a cam 50 on the horizontalshaft 52 of the whirl-actuating connections. The shaft in the machineillustrated is geared to make one revolution for each revolution of thecam shaft in the head of the machine and, therefore, makes one completerevolution during each stitch-forming cycle. A spring 54 holds therocker lever so that its cam roll follows the cam surface.

In order to eliminate any possibility of variation in the amount oftension exerted on the thread which may be occasioned by variations inthe resistance which must be overcome in drawing the thread from thesupply through the wax pot and stripper, mechanism is provided tocooperate with the clamping jaws to pull off the requisite amount ofthread from the supply through the wax pot and the stripper 20 so thatduring each upward movement of the clamping jaws with the thread duringthe loop drawing stroke of the needle, a sufiicient amount of slackthread will be provided for this operation. The pull-off mechanismherein disclosed for drawing oi the requisite amount of thread from thesupply through the wax stripper comprises a bell crank lever 56 which ismounted to swing on a pivot 58 on the machine frame and is provided atits lower end with a pulley 60 which is adapted to engage with thethread between an idler roll 61 above the thread stripper 20 and theclamping jaws 8 and 28. The thread pull-off is actuated in timedrelation to the clamping jaws and other parts of the machine by means ofa face cam 62 formed on the shaft 52 which engages with a roll 64 on theupper end of a bell cranklever 66 loosely mounted to turn on a pivot 68on the bracket 14. The other arm of the bell crank lever 66 is connectedby means of a link 70 to a pin 72 on the pulloff lever 56. A spring 74coiled about the pivot shaft 68 and secured at one end to the lever 66and at its other end to the bracket 14 tends to rotate the lever in adirection'to hold the roll 64 at all times in engagement with the cam62.

In the operation of the machine starting with the parts in substantiallythe positions shown in Fig. 2 the arm 8 is in its depressed positionagainst thestop 42 with the thread tightly clamped between the jaws 8and 28. The pulley 60 is now moved to the right as shown in dotted linesin Fig. 2 to draw ofi thread from the supply through the wax pot and waxstripper and is then returned to the full line position at the left,giving up its thread as the thread is drawn upwardly through the hollowshaft 4 during the loop drawing stroke of the needle 7. Due to theclamping action of the jaws 8 and 28 the arm is moved upwardly with thethread against the pressure of the spring 38 to provide a constanttensioning strain of predetermined amount on the thread throughout itstravel. This tension may be modified by adjusting the angular positionof the collar upon the pivot 10 to wind up or unwind the spring 38. Whenthe rocker 44 causes the aws to be separated and to release the thread,the tension is released and the arms 8 and 28 swinging downwardly intocontact with stop 42 through the recoil of spring 38, and assume aposition in readiness to take a new grip upon the thread at a point moreremote from the stitch forming devices for the repetition of the tensionapplying function. Since there is no relative movement of the threadwith respect to the clamping jaws to run back t action of the spring 38,the tension is mainface, and no slack can develop between the tensiondevice and the stitch forming devices.

lVhat is claimed as the invention is: 1. Tension devices for sewingmachines having, in combination, thread-clamping means adapted to travelwith the thread,

means acting to resistsuch travel, and means acting to disengage andreengage the clamp ing means with the thread.

2. Tension devices for sewing machines having, in combination,thread-clamping means adapted to engage and be carried along with thethread when the latter 1s pulled upon by the stitch-forming devices,means yieldingly acting to move the clamping means reversely to suchpull of the thread, and means acting periodically to disengage andreengage the clamping means with the thread.

3. Tension devices for sewing machines having, in combination, an armmounted to swing along the path of travel of the thread, clamping jawsupon the arm to engage the thread, means tending to move the armreverse'ly to the direction of travel of the thread and yielding to thepull of the thread when the latter is engaged by the jaws, and means forperiodically disengaging and reengaging the jaws with the thread.

4. Tension devices for sewing machines having, in combination, a pair ofthreadclamping jaws movable along the line of travel of the thread,means yieldingly urging the clamping jaws to move in a direction opposedto the travel of the thread, and means alternately freeing the jaws topermit them to move oppositely to the thread under their yieldingactuating means, and then effecting the clamping of the jaws upon thethread at the end of such movement so that ensuing movement of thethread will carry the jaws alongtherewith against the resistance of theyielding actuating means.

5. Tension devices for sewing machines having, in combination withstitch-forming devices including a hook needle, threadclamping meansmovable back and forth along the path of travel of the thread from itssupply to the work, means yieldingly resisting the travel of theclamping means in the direction toward the work, and means for engagingthe clamping .means with the thread to hold back on the thread as theneedle is drawing the latter through the work, and for releasing theclamping means from the thread as the needle completes itsthread-drawing movement.

6. Tension devices for sewing machines having, in combination withstitch-forming devices including a hook needle, of threadclamping meansmovable in the direction of travel of the thread as drawn forward by theneedle, adapted to grip the thread tightly to prevent relative movement,means urging the clamping means reversely of the direction of travel ofthe thread to cause it to exert a tensioning pull upon the thread and totake up any slack, and means adapted to disengage and reengage theclamping means with the thread.

7. Tension devices for sewing machines having, in combination with thestitch-forming devices including a hook needle, of thread-clamping meansadapted to be moved in one direction by the thread as drawn forward bythe stitch-forming devices, spring means adapted to resist such movementof the clamping means and to move it reversely when disengaged from thethread, a cam, and

" means operably combined with the cam and the thread-clamping means fordisengaging and reengaging the latter with the thread in timed relationwith the movements of the stitch-forming devices.

8. Tension devices forsewingmachineshaving, in combination, threadclamping means adapted to engage with and move with the thread, meansacting to resist the movement of the clamping means with the thread, anda thread pull-ofi' to supply slack thread to the thread clamping meansin advance of the movement of the said clamping means with the thread.

9. Tension devices for sewing machines having, in combination, with thestitch forming devices including a hook needle, of thread clamping meansmovable back and forth along the path of travel of the thread from itssupply to the work, means yieldingly resisting the travel of theclamping means toward the work, means for engaging the clamping meanswith the thread to hold back on the thread as the needle is drawing thelatter through the work, and for releasing the clamping means from thethread as the needle completes its thread drawing movement, and a threadpull-ofi to supply slack thread to the thread clamping means in advanceof the movement of the said clampl ing means with the thread.

10. Tension devices for sewing machines having, in combination with thestitch forming devices including a hook needle, and a whirl containinghorn for supplying the 'thread to the needle and a wax stripper throughwhich the thread is drawn from the supply, of thread clamping meansinterposed between the thread stripper and the work movable back andforth along the travel of the thread from its supply to the work, meansyieldingly resisting the travel of the clamping means in the directiontoward the work, means acting to disengage and re-engage the clampingmeans with the ithread, and a thread pull-off interposed between thethread clamping means and the thread stripper to supply slack thread tothe thread clamping means in advance of the movement of the saidclamping means with the thread.

In testimony whereof I have signed my name to this specification.

ERASTUS E. WINKLEY.

